Wachtell, Lipton, Rosen & Katz – which has long been a legal adviser to the CBS Corporation – renewed its 250,000-square-foot lease with the broadcaster at the CBS-owned Black Rock office building in Midtown.

The law firm, widely regarded as one of the most prestigious legal shops in the country, renewed ahead of its 2019 lease expiration for the ten floors it occupies at 51 West 52nd Street, sources told The Real Deal. The length of the renewal was not clear.

A representative for Wachtell Lipton declined to comment. Founding partner Martin Lipton is famous for inventing the “poison pill” defense strategy that corporations use to fend off hostile takeovers. His firm represented Larry Silverstein in legal battle with his insurers over claims at the World Trade Center following the 9/11 terror attacks.

Mitch Steir and Howard Nottingham of Savills Studley negotiated the renewal on behalf of Wachtell, Lipton alongside Moshe Sukenik and Lance Korman at Newmark Knight Frank. Michael Laginestra and Andrew Sussman at CBRE negotiated on behalf of CBS. The Savills brokers declined to comment, and the brokers from CBRE couldn’t be immediately reached.

Financial terms of the deal weren’t available, but asking rents on Sixth Avenue averaged $85 per square foot during the third quarter, according to Newmark Knight Frank.

CBS owns and is headquartered in the 38-story 870,000-square-foot tower designed by famed modernist architect Eero Saarinen, which is known as “Black Rock” for its noir granite façade. Other tenants in the building include Charles Schwab, which occupies 8,000 square feet on the ground floor, and the law firms Dorsey & Whitney and Orrick Herrington & Sutcliffe.

CBS had the tower built as its headquarters in 1965 on what was then known as Broadcast Row due to rival networks ABC and NBC being based in the area. When Viacom purchased CBS in 1999, it reportedly looked to sell the landmarked building for $370 million, but no deal ever materialized. Viacom and CBS split in 2006, and Wachtell Lipton advised CBS in 2016 when talks of merging resurfaced.

For 13 years between 2003 and 2016, Wachtell was named the country’s most prestigious law firm by Vault.com’s annual survey of 18,000 law firm associates.

Correction: A previous version of this story incorrectly stated the length of Wachtell, Lipton, Rosen & Katz’s renewal at 51 West 52nd Street, as well as the number of floors the law firm occupies.